Process for the carbonization of organic cellulosic materials of vegetable origin



May 1939- T. REICHERT 2,160,341

PROCESS FOR THE CARBONIZATION OF ORGANIC CELLULOSIC MATERIALS OF VEGETABLE ORIGIN Filed Dec. 15, 1936 2 Sheets-Sheet} May 30, 1939. RE|HERT 2,160,341

PROCESS FOR THE CARBONIZATION OF ORGANIC CELLULOSIC MATERIALS OF VEGETABLE ORIGIN Filed Dec. 15, 1936 '2 Sheets- Sheet 2 5/0 Wen:

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uurran *srArEs "PATENT mm 1 PROCESS F011. OARBONIZATION ORGANIC CELLULOSIC MATERIALS 0F VEGETABIE carom a 'lheophil Reichert, Brilonwald, Germany, assign or to the flrm of Scheideanstalt,

5 Claims.

My invention relates to an improved process for the carbonization oforganic cellulosic materials of vegetable origin, preferably of some form of wood, but also of similar materials such as nutshells, corn cobs. Deet, lignin and the like.

This application isa continuation-impart of my copending filed December 23, 1933.

It is a well known fact that in the dry distillation of such materials a decomposition reaction occurs'at a certain temperature which is highly exothermic. At this point in the process a sudden and large rise in temperature occurs.

This increased temperature causes undesirable decomposition of a large part of the valuable distillation products present in the wood, and thus decreases the yield of such products. Numerous efiorts have been made to avoid this effect, but none of them have been successful.

I have found, surprisingly, that this decomposition of the distillation and higher yields obtained by a special manipuexothermic reaction of the lation of the carboni zation process.

The principal feature of my discovery is that decomposition of this kind can be largely avoided if the material is heated from the top downwardly in the proper manner. In other words, the'material is carbonized by hot gases which are introduced or to be carbonized and drawn the lower part of the mass in the carbonization progresses from the top downwardly, so

downward through such a manner that gradually in zones that simultaneous entire contents of themass is avoided.

According to a particular feature of the invention, the wood is carbonized by passing hot gases, which are properly tempered, from the top downwardly, in such a manner and at such a velocity that the zone-wise carbonization takes placebeginning at the top. In other words, the

temperature and velocity of the heating. gasesv are so chosen that the upper layers are carbonized and then'gradually this carbonization proceeds downwardly through the mass.

The process can be performed in many various types of retorts. Horizontal, vertical or inclined retorts maybe used. In all these types of apparatus, heat losses should be avoided by insulating the retort. I

The preferred manner of practicing the process consists in preheating a gas which does not contain free or uncombined oxygen and then drawing such heated gas downwardly through the material. The vaporous distillation products ob- Application December 15, 1936, Serial No;

In Germany December 24, 1932 application, Serial Number 703,816,

- regulationof heat is much products can be avoided formed at the top of the mass Goldand Silber tained from the wood pass downwardly with the heated gases and are drawn oil at or near the bottom of the retort. I have found that in order to produce step-wise carbonization it is neces sary that the rate at which the heating gases are 6 passed through the wood should be between 1 and 3 cubic meters of gas per kilogram of wood per hour. Inthe preferred form of the invention from 1 to 2 cubic meters of gas are used per hour for each kilogram of wood. 1

Instead of using preheated gas, however, it is possible to burn a combustible gas Just above or in the top of the heating chamber, while avoiding carefully any excess of oxygen, so that no free oxygen will be present in the gases. of using gas as a'fuel, coal-dust or oil might also be used. The use of gas is preferable as the easier with a gaseous fuel.

The process may also be carried out by heating 20 the upper layers of the materials to be carbonized to an oxidation temperature in the presence of air or oxygen, thus producing hot gaseous products. These may be drawn through the material at a rate dependent onthe supply of 25 air to the upper layer, and preferably'at such a i rate as to provide oxygen-free gases in the proportion specified above. .Another manner of carrying out the process is to heat the upper layers so as to produce gaseous distillation prod- 80 ucts which may be drawn -down through the remainder of the material and themselves act as heating gases.

The method of operation above described produces a. progressive heating from top to bottom through the mass and thus a progressive car- .bonization. Each portion of the mass beginning with the top layer is first dried and then carbonized and the gaseous products driven out.

Inasmuch as the gaseous productsfrom any part 40 of the material are drawn downwardly immediof lower temperature, they are p to this lower temperature and are subject to the carbonizing temperature only for a short time. In this manner any'excessive decomposition of the products by long exposure to the carbonizing temperatureis avoided. Upon entering the lower zone the heat of the reaction is absorbed by'the relatively cool ma-' terial still to be treated and thus the gases or gaseous products are cooled immediately. At the same time, the flow of gas is not so rapid as to cause carbonization of the lower layers before the upper layers have been carbonized.

According to a further feature of the invenately into a zone subjected at once Instead 15 Y tion, some of the gases issuing from the retort, this column. A pump I8 is provided which will preferably after the distillation products have force either tar or tar-oils through a pipe 20 to a been recovered from them, may be recirculated spray 22 in the top of the column IS. The tarthrough the retort either alone or together with oils are drawn off at the bottom through a pipe hot fresh gases. Furthermore, some of the 24 and returned to the pump. An outlet pipe 26 evolved gases may be burned to supply heat to may be provided at the bottom of the separatin the circulating gases. column through which excess tar may be re- The process can be performed periodically, moved.

semi-periodically or continuously. With periodic It is also desirable at times to supply steam to operation the carbonization process can be permix with the gases passing'through this column. formed fractionally. This steam may be drawn from a line 28 and One essential requirement of the process relates supplied through a pipe 30 to the bottom of the to the temperature and the rate of circulationof column l6.

the heating gases. The rate of circulation of the From the top of the column IS the gases may gases should be sufficiently high so that there is pass into a small chamber 32 filled with tar or no appreciable condensation of the condensible any liquid to avoid gases from flowing back in constituents driven off from the wood in the the case that the pressure of gases before said layers below the zone inwhich carbonization is chamber should decrease. From the chamber 32 taking place. In other words, while the gases the gases pass through a pipe 36 to the top of a must be immediately cooled to prevent further. condenser 38. The gases pass downwardly decomposition by the heat of carbonization, through the condenser through tubes 40, the nevertheless they should not be cooled to such space around these tubes being supplied with a an extent as to produce condensation of the concooling liquid through inlet pipe 42 and exit pipe d'ensible constituents thereof. On the other hand. 44. The bottom of the condenser is provided it is important that the rate should be sufliciently with an outlet 48 to permit the withdrawal of the low so that the mass is heated gradually or in condensate therefrom. Crude acetic acid and layers or zones to the carbonizing temperature. some crude wood alcohol are thus separated out.

If thejgas is introduced too rapidly, then the From the bottom of the condenser a pipe heat is carried down into the lower zones and leads the remaining gases to the bottom of a all will be carbonized at substantially the same scrubber 50. This scrubber is filledwith porous time. Thiswould mean that any gases which are material 52. The gases pass upwardly thereevolved in the upper layers would not be cooled through in counter-current relation with water and would be subjected to a considerable period which is pumped by a pump 54 through a pipe of high temperature; and thus the distillation 56 to a spray 58 adjacent the top of the column. products would be likely.to be decomposed. and The water is returned through a pipe '60 to the the beneficial eifects oi. the process would be pump. If desired, steam may also be introduced t through the line 52 from the line 28 into the The apparatus which is disclosed is particubottom of the scrubber, and the water and wood larly suitable for carrying out the process above spirit which are washed out may be withdrawn generally described. A separately through outlets 64 and 6B. Further objects and advantages of the'inven- From the scrubber the gases pass through 2. tion will appear more fully from the following pipe 68 to the bottom of a second scrubber I0. description, particularly when taken in conjunc- This scrubber is also supplied with water from a tion with the accompanying drawings which form line "through a pipe I4 to a spray I6 within a part thereof. the scrubber. The water from the bottom of the In the drawings: scrubber is withdrawn by a pipe 18 to the pump Fig. l is a diagrammatic showing of an ap- 54. Any excess water may also be taken f! paratus" for carryingout the invention. through the outlet 80. Wood spirit and the Fig. 2 is a diagram showing an apparatus in soluble volatile constituents are removed in these which three or more carbonizing retorts may be scrubbers. used. A pipe 02 leads from the top of the scrubber 10 The invention will be readily understood from a to conduct the gas to blowers 84. These blowers description of the accompanying drawings showand a system of pipes and valves 86 permit the ing an apparatus in which this process may be distribution of the gas to either of two pipes carried-out. and 90. The pipe 90 leads into a main 92, while As shown in Fig. 1, the apparatus includes a thepipe 00 leads the gas to a preheating arcarbonizing retort 2. This retort may be opened rangement 94 now to be described. and closed at the top as at l to permit filling Gas from the main 92 is supplied through a thereof. The upper wall section 6 and the lowerpipe 96 to the preheating arrangement 94. At wall section 0 are in the form of frustums of the same time, an air pump 98 pumps air through on cones. An important feature of the invention is pipes I00 to this device. In the preheater, the that the top wall section 6 must be at a greater gases furnished by the pipe 96 and the air furangle of inclination or more nearly vertical than nished by the pipe I00 are burned together in the the lower wall 8, their angles being 57 and 45 space I02. This space is of -a serpentine nature. respectively. As is shown by the drawings, the and the gases flow therethrough as they are 5 walls of the retort 2 are insulated to prevent the burned and come out at I04, from which they escape of heat therefrom. Materials such as can pass out of the preheating device through a the carbonized wood may be removed from the flue I06. The gases in pipe 88 on the other hand bottom of the retort through an opening I0 or pass through the smaller pipes I08 inside the in any other suitable fashion.

At the bottom of ,tlieretort is arranged a reburned in the pipes I02. These preheated gases ce e l2 i o wh t 88- 8 Pas F om the pass out through pipe 0 to a valve 2 arranged receiver I2 the gases p th ough a line H o a at the ta er the carbonizing retort 2. Thus the tar separating column I8, for removing tar-like gases produced in the retort are first cooled and constituents. The gases enter near the bottom of washed' so that all the condensible constituents 15 are removed and are then returned, after preheated, and passed again through the retort v in a downward direction to cause iurther carbon ization of the wood. I

If desired, steam may also be supplied from the main 28 through the pipe Ill to aspray H8 in the top of the retort 2. This is used to remove any residue of volatile products during or after the carbonization.

be-carbonized, as ior'instance the wood of deciduous trees, and hot gases from any suitable ,source, such as'from another retort oi the same type, are introduced through valve 2 into the top of the retort. These hot gases pass downwardly through the retort and out through the pipe I. The gases first dry the wood and any water-which is evaporated-passes oif with'the gases through the outlet l4. L

. As soon as the wood is dried,".the hot gases which pass downwardly through the wood begin toicarbonize the same. These preheated gases drive out thedistillation products from the wood and carry them downwardly. Tl'lese gases pass out through the pipe I to the various partsor the apparatus described above. Such of the gaseous .constituentsas are of a tar-'likenature are separated in the tar separating columns l6.

The condensible constituents are condensed and separated in the column 38. Other volatile or soluble constituents are washed out in the scrubbers 50 and III. The remaining portion of the gases, which have a high fuel value, is pumped by the blowers '84 through the pipe ystem 88. to various points of use.

A certain portion of the gases are pumped through the pipe 88 and then through the preheater pipes I08 to the top of the retort. Some of the other gases are pumped into the line Q2 and then through pipe ll to the outer preheater pipes I02 where they are burned to heat the gases flowing through the inner pipe. The gases to be supplied to the retort are thus preheated by the burning of some of'the products oi the heating of the wood.

The gases introduced at the top of the retort 2 preferably have a temperature ofbetween 500 C. and 600 C. The circulation of the gases is carried out at such a rate by means of-the blowers and valves that the quantity-oi gas flowing through the retort is between .1 and 3 cubic meters of gas per kilogram of wood in each hour. Preferably, the quantity is between 1 and 1.8 cubic meters. By this procedure the gases comhis out atthe bottom of the retort are at a relatively low temperature. During the greater part .of the carbonization, the temperature of the escaping gaseous products is only about 80 C.,- although, when the carbonizing .zone approaches glae bottom 01' the retortit may rise as high as By varying the amount, of the recirculating gas within the limits specified, it .is possible to'obtain varyingresults. For example, the amount oftar produced can be varied so that more valuable products are obtained.- Inasmuch as the circulating gases contain wood alcohol, an increased formation ofesters takes place. Further more, the carbon content of the charcoal may be regulated so that itis possible to obtain aproduct containing 90% carbon. I g

The procedure above described has numerous advantages; A recirculation of the gases 'makes it possible to'use a great proportion of the heat developed-since this heat is used for the heating of furtherfgases. In this way the external'heatingrequired by the process is considerably re- ,duced. (Furthermore, the yield of acetic acid is increased, it being possible to obtain as much as 42 kilograms from the same amount of wood from which previous procedures had only yielded 32 kilograms.

It will thus be seen that the essential feature of the'invention resides inpassing the vaporous products from the wood with the hot gases downward immediately at a suitable rate of flow into a coolerzone where they are not subject to further decomposition. In this manner, the heat developed by the exothermic reaction'is used in a sense to preheat but not to carbonize the lower layersof material.

In the form of the invention shown in Fig.2, I have shown how-three carbonizing retorts may advantageously be used simultaneously. During the time that one of these retorts 2a is being operated to, carbonize wood. the contents of the:

second rtortt2b may be prepared by treatment with hot gases to obtain a charcoal with increased carbon content, while the third retort 20 is-being charged. The gases from one retort may be used in another through pipes I20, either as drying or. heating gases or forany'other purpose. While l' -have described herein some embodi-' ments of my invention, I'wish it to be understood that I do notintend to limit myself thereby except within the scope of the appended claims. I claim:

1.v A- process for the dry distillation of organic cellulosic distillable material of vegetable origin, in a retort heated internally only, which comprises supplying a hot gas at the top of a bed of such material of substantial depth within said retort to distill the material destructively while avoiding decomposition of the volatile substances evolved from the material 'by heating, passing said gas while still hot downwardly through the material in the retort at a rate of between 0.1 and 3 cubic meters .per hour per kilogram of the material to be carbonized, the gas being fed at such a velocity and in such a quantity that the carbonization of the material proceeds gradually downwardly, that the temperature difference throughoutthe mass is maintained low, and that condensation of the evolved volatile substances in the lower part of the material is substantially prevented, and recoverin distillation products from such gas.

2. A process for the dry distillation of organicv cellulosic 'distillable material of vegetable origin,

in a retort heated internally only, which vcomprises supplying a hot .gas at the top of a bed of such material of substantial depth within said retort to. distill the material destructively while avoiding decomposition of the volatile substances evolved from the material by'heating, passing said gaswhile'stillhot downwardly through the material in the retort at a rate of between i and 1.8 cubic meters per hour per kilogram of the material to'be carbonized, the gas being fed at such a velocity and in such a quantity that the carbonization of the material proceeds 4 gradually downwardly, that the temperature difference throughout the mass'is maintained low,

and that condensation oi; the evolved volatile recovered to the-top oi the andscubicmetersperhourpergilogramoithe of such material of substantial retort to distill the 7 evolved fromthe material by heatins. p s ingsaid gas while still hotdownwardly through the material in the retort at a rate of between 0,1 and '3 cubic meters per hour per kilogram of the the gas being led at such a velocity and in sucha quantitythat the carbonization oi the material proceeds gradually downwardly, that the a temperature difference throughout the mass is maintained low, and that condensation of the evolved volatile substances in the lower part oi the material is substantially prevented, recovering distillation products from such gas, and returning at least a part of the gas from whichdistillation produ ts have been retort. 4. A process for the dry distillation 0! organic cellulosi dlstillable material of vegetable origin, in a retort heated internally only, which comprises supplying a'hot gas to the-top of a bed of such material of substantial depth within said destructively -while avoiding decomposition oi! the volatile substances evolved from the material by heatlnlspass ng 'said, gas while still hot downwardly through the material in the retort .the top of the retort.

ting condensible material to be carbonized, such a velocity and in such a quantityv that the the gas being fed at carbonization oi the material proceeds gradually that the temperature diflerence and that prevented, removing condensible constituents from such gas, heating at least a part of the gas from which the condensible constituents have been removed, andreturning such hcatedgas to 5. A process for the dry distillation of organic cellulosic distlllable material of vegetable origin,

internally only, which com in a retort heated prisessupplying a hot gas to the top oi-a bed of such material or substantial depth within f while avoiding decomposition of the volatile substances evolved irom the material by heating. passing said gas while, still hot downwardly through the material in the retort at a rate oi between 0.1 and 3 cubic meters per hourper kilogramot the material to be carbonized. the gasbeing fed at such a velocity and'in such a quantity that evolved volatile the material is c'onetituentsirom such gas. burnina a portion dens'ibie constituents have been removed and utilising the heat thereof to preheat a second portion of the gas. and returning such heated portion to the top oi the retort. Y

mommoi the mate-' of the gas from which con- 

